The current set resistor (between OUT and ADJ) would consume about 1.25V*5A=6.25Watts of power.
I want to use a potentiometer here since I want to be able to adjust the output current.
This is where I no longer like this setup, but I don't know what other possibilities there are.

Is there any other way I can easily regulate currents up to 5A, with a linear regulator?

Kind regards

EDIT:
If we are going to use another IC for this, I'd prefer one which has an enable pin because the laser diode
must be controlled by Arduino to go on and off at regular intervals (about each 200ms)
It does not necessarily need to be an enable pin, but just any way of toggling the output.

It would also be great if I could control the current trough Arduino.
All I can come up with are these two possibilities:

A digitally controlled potentiometer, but I can't seem to find low resistance values (below 1ohm) or high power (above 5W) so I don't think this will be an option.

My second thought was using a transistor as variable resistor, but how will I power the base with Arduino? I'll still need an analog voltage output, which the Arduino doesn't have.
In what ways can I control a transistor in it's linear operation mode, trough Arduino?

It would also be great if I could control the current trough Arduino.
All I can come up with are these two possibilities:

A digitally controlled potentiometer, but I can't seem to find low resistance values (below 1ohm) or high power (above 5W) so I don't think this will be an option.

My second thought was using a transistor as variable resistor, but how will I power the base with Arduino? I'll still need an analog voltage output, which the Arduino doesn't have.
In what ways can I control a transistor in it's linear operation mode, trough Arduino?

That looks like a decent IC. I think that should work.

You don't need a low ohm potentiometer. The way scaling/gain works on those ICs well typically allow you to use 1k pots (or higher). Start building the circuit with standard fixed resistors, and you'll see where the pots can go. You don't vary the sense resistor in this type of setup.

If this is for a hand held, a AMC7135 based driver like the Nanjg 105C driver should work.

You would need to stack 6 to 7 more 7135's on a 2.8 amp driver to get to 5 amps. Each chip allows 350mA of current. They "burn" off excess voltage in the form of heat. So you would probably want 1S Li-ion voltage level for input. You need at least .1 volts overhead (after voltage sag) for regulation.

There are also several AMC 7135 based circuit boards you can purchase from OSH Park if you need a different form factor than the Nanjg 105C.

If this is for a hand held, a AMC7135 based driver like the Nanjg 105C driver should work.

You would need to stack 6 to 7 more 7135's on a 2.8 amp driver to get to 5 amps. Each chip allows 350mA of current. They "burn" off excess voltage in the form of heat. So you would probably want 1S Li-ion voltage level for input. You need at least .1 volts overhead (after voltage sag) for regulation.

Ok so the diode is droping 2 Volts at 5 amps ( read 2.2V for some reason ) so that's 10W , but the worst case as per the data sheet is 2.2V (11W ) so the maths in my last post still works , so long as the diode drops 2.2V at 5A :P

Well that's 780mW per IC if there are 14 of them , based on a 2V diode drop , 2.2V regulator drop , 350mA per regulator

__________________
I don't know what you had in mind
But here we stand on opposing sides .

and the fact that it will be controlled by an Arduino suggests it will be used as some sort of CNC cutter? or similar application.

Quote:

Originally Posted by FalloutBe

I'd like to make use of a linear regulator, powered by a 5V, 8A switched mode power supply. (link)

<snip>
EDIT:
If we are going to use another IC for this, I'd prefer one which has an enable pin because the laser diode
must be controlled by Arduino to go on and off at regular intervals (about each 200ms)
It does not necessarily need to be an enable pin, but just any way of toggling the output.

No Li-ion cell is going to hold 4.2V under a 5 amp load. Best would probably be 3.9v. Also, the 7135 consumes .1 v. So 1.6 volts (3.9 - 2.2 - .1) to burn off.

But, I do agree that that is a lot of voltage to burn off. I miscalculated in my head when I replied. I was thinking it was an under 1 volt difference. AMC7135 might do if he is powering by 2SxP Eneloops.

First of all, thanks for all the effort and suggestions!
But I'm going to come in between your calculation battle for a moment now, to clear out some misunderstandings.
Also, I don't think using 14 350mA regulators is a good idea. It might work, but .. .seriously? that's ridiculous..

The laser will not be handheld, it'll be used for CNC engraving, like djQUAN assumed.
It will indeed be powered by a 5V 8A supply, which I already ordered.
I also ordered the LT1083 and I still think it's a good idea to use that one.

Let's do some power calculations on the components:

2.2V*5A=11W laser diode.

The regulator uses a fixed 1.25V reference, so there we'll have 1.25V*5A=6.25W dissipating in the 'current set resistor' (located in between OUT and ADJ)

Supply was 5V, so what's left is 5V-2.2V-1.25V=1.55V
*5A=7.75W power to be dissipated in the LT1083
According to the datasheet, a maximum of 60Watts can be dissipated in the chip, so that's perfect.

After some thinking, this is what I'm planning to do for now (see attached image)

The idea is to put the laser in front of the regulator, instead of behind it. I don't think this should cause any problems; it's just components in series, so I can switch them around, right?

This, I do to make sure I can connect the source of the MOSFET to ground, so that I can easily control it from the Arduino microcontroller.

The gate voltage of the MOSFET will be set by the RC filter, which is set by a PWM output of a digital pin.
The RC filter will convert the PWM signal into a smooth DC voltage.

The MOSFET has a 0.25ohm resistor in series, to make sure the maximum current is limited to 5A, when the MOSFET is fully conducting.